OK, let's do this. We've got 7233 and 5515 and we're adding them all together.

Step 1: We'll start by adding the digits 3 & 5 in column 1 and get 8.

Step 2: We'll start by adding the digits 3 & 1 in column 2 and get 4.

Step 3: We'll start by adding the digits 2 & 5 in column 3 and get 7.

Step 4: We'll start by adding the digits 7 & 5 in column 4 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 7233 + 5515 = 12748.

